In Situ Study of Lithium Plating and Stripping Dynamics on 2D Carbon Surfaces

Anode-free lithium metal batteries offer exceptional energy density but face challenges due to lithium dendrite formation. Achieving uniform lithium plating is crucial to address this issue, yet it remains unclear whether the current collector should be lithiophilic or lithiophobic. In this study, we present a comparative in situ atomic force microscopy (AFM) investigation theoretical and density functional theory (DFT) analysis of lithium plating and stripping dynamics on a bare copper current collector and copper coated with monolayer graphene, whose basal plane is lithiophobic, and monolayer amorphous carbon (MAC), which is lithiophilic.
Our findings reveal that MAC exhibits an extremely high initial nucleation density and a low nucleation overpotential (NOP) due to its amorphous structure. However, under steady-state conditions, MAC shows a lower apparent nucleation density compared to Cu and Cu with graphene. This counterintuitive reversal of the nucleation density is a common phenomenon for lithiophilic surfaces and aligns well with theoretical predictions but experimentally has never been reported before. We also observe that the solid electrolyte interphase (SEI) formed on MAC is softer, and merging of lithium deposits occurs during the second cycle.
Our theoretical modelling, mechanical analysis of the SEI, and in situ AFM studies of lithium plating dynamics highlight the importance of lithium atom exchange within the SEI and the interplay between current collector coatings and SEI engineering in designing advanced lithium metal batteries.